There is increasing demand for reliable techniques which allow obtaining the location of a user of a telecommunications terminal. In fact, with the marked expansion in location-based services (LBS), we are seeing increased user demand for a rapid determination of their location in a precise manner and with a low failure rate.
Frequently used location solutions are:                those based on satellite systems,        those based on mobile networks, and        those based on the Internet.        
Location solutions based on satellite systems, such as the American GPS (Global Positioning System) system, are used by terminals equipped with GPS receiving means that can decode the synchronization signals sent by the satellites in order to deduce their position, subject to visibility by at least three satellites. Due to this, although this method is effective in terms of accuracy, it only works in certain types of environments (where the sky is directly visible) and with a limited number of terminals.
In location solutions based on mobile networks (GSM, UMTS, etc.) or local area networks (WLAN, for example WiFi), determining the location of the mobile terminals is based solely on two principal mechanisms such as:                using indications of the strength of the signals received, and        using the identifier for the cell to which the terminal is connected.        
In the first technique given above, indications of the strength of the signals received from fixed transmitters or access points or base stations (RSS technique, for “Received Signal Strength”) are used. Several location methods have been developed that are based on this received signal information. The most common is based on creating a database of RSS vectors corresponding to a spatial discretization. The principle of this method, commonly called calibration (or fingerprinting) or sampling, is:                to find the best correspondence between the RSS vector measured by the mobile terminal (signal level measured at a given location) and those stored in a database, then        estimating the location based on this correspondence.        
This method must necessarily be accompanied by a continuous exchange between the terminal and the dedicated server hosting the correspondence database in the network.
The second of said location techniques uses the identifier of the cell to which the mobile terminal to be located is connected. In fact, each mobile terminal “grabs” a cell in order to exchange data or send/receive voice calls via the mobile network. Each cell corresponds to a base station or access point for which the coordinates are only known by the equipment in the network. Due to this, in order to find out its location, a mobile terminal must send the cell identifier (for the cell where it is located) to a dedicated platform in the network. This platform returns the position associated with the base station to the mobile terminal. Several disadvantages result from this arrangement:                imprecision (compared to other location techniques), and        high latency times (due in particular to the response time of said platform).        
Internet-based location solutions, which use the IP address associated with the user terminal (PC or mobile), make use of mechanisms which allow associating an IP address with the location of the last public router for which the location is known in the Internet wide area network. Due to this, the accuracy is clearly still less precise than values obtained by techniques such as those presented above. The level of accuracy typically is regional (or departmental in France), in cases where the location can even be obtained.